Process for color stabilization and hydrodesulfurization or cracked gas oils



J. H. R. DAVIS JR.. ETAL 3, PRQCESS FOR COLOR SI'ABILIZATIUN ANDaynaoossuwuammu OR CRACKED GAS OILS Filed Sept. 12. 1960 m ms 0 v in FT. a ms... 7 WW2! 6 m .P M M 00 0| 7 I W lw 8 mm e 9 O p m. m e m M a I,0 nl ow EL 0 h a O r. a s o b E n o t w B 0 G 0 f 0 .m m m m m R w r wHm M m I o o c N F d w A [W o 6 o O o. o r. i 7 B. 5 4 4 0 m Ev n. 83 5226 22 a m 28 53 m I 1m 2 8 II 6 0 IL n b M Ma! .Im a. o 6 map pl- 0 F mma m r o M m% M 5 aw a O 0 4D 0 C I o h M 5 M LN & l on! G F E RIN C RQML +z l 76 L is w m 3 Q "a; o .1 ca A A .m 0 cu m 0 m 0 0 M o 3 2 .1 0gN w w 2 .385 B 5 m 55m J Dec. 22, 1964 E 2 0 2 m 0 zHmd ATTORNEY UnitedStates Patent l PROCESS FOR COLOR STABILIZATION AND HYDRODESULFURIZATIONOR CRACKED GAS OILS Joseph Hill Rogers Davis, Jr., Rose Valley, and EarlM. Honeycutt, West Chester, Pa., assignors to Sun Oil Company,Philadelphia, Pa., a corporation of New Jersey Filed Sept. 12, 1960,Ser. No. 55,263 Claims. (Cl. 208-416) This invention relates to animproved process for upgrading petroleurn fractions. It especiallyrelates to the catalytic desulfurization and color stabilization ofcracked gas oils. More particularly, it relates to a liquid phasehydrogenation process which utilizes very mild conditions with nohydrogen recycle.

It is desirable to desulfurize catalytic gas oils in order that they canbe used as home heating oils or furnace oils." It is further necessarythat the furnace oils have a clear, light color which can be maintainedover long periods of storage. These requisites and others have beendemanded by the buying public and efforts to de sulfurize cracked gasoils are well known in the art.

One of the most widely used processes for desulfurization is one inwhich the petroleum fraction is contacted with concentrated sulfuricacid. Unfortunately. however, this acid treatment degrades a portion ofthe charge stock by forming sulfonates. polymers. and the like. Theseundesirable compounds are usually removed by subsequent. usuallyexpensive, distillation of the acid treatel product. The heating of therefined petroleum oil in order to distill it has the furtherdisadvantage of decreasing the color stability of the oil.

With the increasing use of high sulfur crudes such as Middle East andVenezuelan crudes, the cracked gas oils have become troublesome todesulturize due to their high sulfur content. The sulfur content ofthese cracked gas oils may be as high as 3% or higher, and the Sulfurshould be reduced to around 1.0% or less, preferably around 0.3%, beforethey are salable as furnace oils. These gas oils may be desulfurized byanother Widely used process-catalytic hydrorefining. However,temperatures in excess of 700 F. are required, together with pressuresof from 650 p.s.i.g. and up. Even at these high temperatures andpressures, it is necessary to hold the liquid hourly space velocity to2.5 vols/bulk volume of catalyst per hour or less in order to secure asatis factory degree of desulfurization.

Further. the hydrorefining of cracked gas oils, while reducing sulfurcontent, has an extremely undesirable tendency to destroy the lightcolor of the oil and still further, to destroy the oils ability tomaintain a pleasing, satisfactory color upon aging. In addition to a lowsulfur content, a cracked gas oil in order to be salable as a furnaceoil, should have an ASTM color, initially, of less than 1.0, preferablyless than 0.5, and after storage, at 110 F. for six weeks, should havean ASTM color of less than 2.0.

it is an object of this invention to provide an improved method forreducing the sulfur content, improving the initial color, and increasingthe color stability of cracked gas oils. It is a further object toprovide a desulturization process that has increased eificiency for theremoval of sulfur from such oils.

We have found that the foregoing objects may be attained by contacting,in an atmosphere of hydrogen, the sulfurcontaining cracked gas oil inliquid phase with a sulfur-resistant hydrogenation catalyst at atemperature which is controlled within relatively narrow limits. Wefurther have found that the efficiency of sulfur removal can be improvedby blending a relatively high sulfur content cracked gas oil with arelatively low sulfur content cracked gas oil and passing the blend overa sulfurresistant hydrogenation catalyst as mentioned hereinabove in thepresence of hydrogen. According to the present invention, the relativelyhigh sulfur content material must contain 0.5% to 50%, preferably 0.8%to 1.36%, more sulfur than the relatively low sulfur content" material.

The term cracked gas oil is defined herein as any petroleum fraction ofgas oil boiling range derived from thermal or catalytic cracking ofhydrocarbons. It includes those petroleum fractions so obtained whichboil mainly between 425 F. and 700 F. and which contain at least 0.3%sulfur. By hydrogen is meant any hydrogen-containing gas which is40-l00% free hydrogen, preferably, between 70100%. It can be mixed withinert diluents and can be derived from other refinery sources such asreforming units. Recycle hydrogen gas is not required for this process.The term atmosphere of hydrogen as used herein denotes that there is nonet flow of hydrogen through the Contact zone other than the smallamount which dissolves in the liquid effluent.

The process conditions require a temperature between 500 F. and 675 F.,preferably between 550 F. and 650 F. The pressure may range from about300 pounds per square inch gauge (p.s.i.g.) to about 1,000 p.s.i.g.,preferably between 500 and 800 p.s.i.g. Liquid hourly space velocitiesof from about 0.5 to 10, preferably 1 to 6 are satisfactory. It shouldbe noted that the choice of operating conditions will be determined bythe charactcristics of the charge stock such as boiling range, sulfurcontent, degree of unsaturation, etc., the desired properties of theproduct such as sulfur content, initial color, color stability, sludgeformation, etc., the purity of make-up hydrogen, and other well-knownconsiderations.

According to the present invention, the cracked gas oil is heated to thedesired reaction temperature, say, 600 F., and passed into a reactor inwhich it trickles downwardly over a sulfur-resistant catalyst. Hydrogenpressure of, say, 650 p.s.i.g., is maintained over a liquid level in thebottom of the reactor. and the hydrogen is admi tted in an amountsufficient to make up for the hydrogen consumed in the desulfurizationof the feed. This amount may vary from 25 to 500 ftF/barrel of feed. Thereaction products are removed from the reactor and are passed to afractionator or separator where the hydrogen sulfide and dissolvedhydrogen are removed. The resulting products which are recovered fromthe fractionator include high octane gasoline and a substantiallydesulfurized cracked gas-oil of improved color and increased colorstability. Usually, the octane number of the gasoline produced is withinthe range of -95 Fl clear octane number.

Any suitable sulfur-resistant hydrogenation catalyst can be employed inthe practice of this invention. Examples of suitable catalysts aremetals such as copper, zinc, mercury, tin, vanadium, tungsten, chromium.molybdenum, manganese, cobalt, iron, nickel, platinum, ctc., oxides ofsuch metals or combinations of such metals or oxides or sulfidesthereof. Any suitable catalyst support can be employed, e.g., activatedcarbon, alumina, aluminum silicates, bauxite, charcoal, clay,kieselguhr, magnesium, pumice, silica, silica-alumina compositions, andthe like. The preferred catalyst is cobalt molybdate supported onalumina. When the term cobalt molybdate" is used herein, it denotes amixture of cobalt and molybdenum oxides which may or may not be in wholeor in part chemically combined.

FIGURE 1 of the accompanying drawings illustrates the effect of reactortemperature on initial color. aged color, and sulfur content of acracked gas oil obtained from Middle East crude. FIGURE 2 demonstratesthe effect of reactor temperature on the color stability of cracked gasoil. FIGURE 3 illustrates the advantage: gained by blending a relativelyhigh su!fur content cracked gas oil :md processing the blend ashereinabovc described.

The present imcntion is based on the discovery that color stabilizationand substantial desulfurization oi? cracked gas oils is. possible onlyover a narrow range oi temperatures, i.e., the temperature isparticularly critical .A temperature too low can impart a :zood initialcolor to the product oil bu the product oil will not be color stahl. andwill not be nirterially dcsulfurized. As the temperature is increased,desulfurization is increased while initial color remains good and colorstabilitv is increased. Be yond a certain temperature (which temperaturedepend. upon the other operating variables and charge stock prop crties)initial color gradually darkens with increase in tem perature, whiledesulfurization continues to increase.

is noted in FIGURE 2, that the color tability rating is maximum at 550F. for the Middle East cracked gas oil. It is also noted thattemperatures between 500 F. and 675 F. produce gas oils havingacceptable color stability. While col r stability may also besatisfactory at temperatures below 500 F.. according to FIGURE 1, suifurremoval would not be, e.g., product sulfur content is greater than 1.0%.Temperatures above 675 render the product unacceptable as a salablefurnace oil even though the sulfur content may be reduced to 0.27% (at700 F). At these higher temperatures, color and color stability areunsatisfactory. For examp e, at 700 F. the initial product is 1.50 andthe aged color is 2.50 giving a color stability index of 5.5 compared toa color stability index of 6.75 at 550 F. reactor temperature.

EXA MPLE 2 A catalytically cracked gas oil from Venezuelan crude wasprocessed as in Example I with the following results:

Venezuelan Catalytic Gas Oil Hyrlrorcfining Conditions Further increasein temperature resul s in excessive dark-- ening of the initial and agedproduct color and a decrease in sulfur removal. Thus, there is a narrowrange of tom-- peratures with which sulfur removal is substantial,initiai product color is light, and color stability is acceptable If theoil treated is relatively low in sulfur, and color improvement andstability are the chief goals. then I wider rang of temperatures may hesed. These advan tages are illustrated in the following examples \\hichar. olfered in order that the invention may be more fully understood bythose skilled in the art.

EXAMPLE I A catalytically cracked gas oil from Middle East crude.boiling between 435 F. and 675 F, was contacted with a cobalt molybdatcsupported on alumina catalyst in the presence of hydrogen of 100% puritywith the following l! addition of tie 1,000 bill.

NtllCO .50.; Ac inhibitor.

The. above data further demonstrate that temperatures above about 650 F.tend to destroy initial and aged color even though the sulfur content ofthe product is fu ther reduced. Further, temperatures between about 550F. and about 6 F. must be adhered to if a product is to be obtainedwhich has a better initial color than the charge stock and has asubstantiallv reduced sulfur content.

Another product quality factor is itlustrated in the above examples,namely, filterable sludge. It is noted that the amount of filterablesludge, by which term is meant the sludge that can be removed byfiltration, is also dependent upon reaction temperature and it isfurther noted that the sludge level is at a minimum betweenteriiperatures of about 550 F. and about 675 F. This is another factorin establishing these temperature limits as being critical in theoperation of this invention. Clearly,

results: beyond a temperature of about 700 F.. further increase MiddleEast Catalytic Gas Oil Hyclroi'alfm'fmtion Conditions Temperature, FCharge 400 55 075 700 7125 Pressure, p.s.i .g 050 650 050 650 650 650LHSV,v./hr./v 3 3 3 3 3 3 Wt. percent sulfur 1. 66 1. 0. 85 0. l0 0. 380. 27 0. 25 Percent S.rciu0val T T2 77 84 85 Initial Color, ASIM 0-15001.25 0.50 0.25 0.25 1.00 1.50 2.0 Aged ti wks. at110 F.21

ASTM 0-1500 Color a. 00+ 2.25 1.25 1.50 2.00 2.50 3.00

Filtcrable sludge, rue/100 ml ti. 5 2. 5 0. 0 0.7 0.5 0.5 1.0

1 With addition of Bit/1,000 bhl. laradyne Il0-4 inhibitor. Theseresults are graphically illustrated in FIGURES 1 in temperature sharplyincreases the amount of filterable and 2. Note that the initial color ofthe product increases sludge in the product. sharply when a reactortemperature above about 625 F. Therefore, according to the presentinvention, operating is used. Aged color is similarly affected. Also.note that conditions must be as follows: the critical temperature rangeof 500 F. to 675 F. must be adhered to if the initial color of theproduct is to be 5 i below 1.0, aged color of product below 2.0, andsulfur tgffigg content less than 1.0%. For this charge stock. thepreferred temperature is 625 F. whcrewith product initial 0 Sana-J55501650 color is 0.25, aged color 18 1.5, and sulfur content is 0.46.Pressure. 0 1s.. 5 0800 Using the above data, FIGURE 2 was plotted toillus- 5mm villi H) trate the effect of temperature on color stability.For T1115 mvemlon, Color slflblllly" Fm 000000 8 the Further, thebenefits of this invention are only obtained aged color of the chargestock minus the aged color of the if th lf t t f h kd il Charge t kproduct. Thus, the higher the index number. the better is at least 0.3%sulfur, and the benefits are most if the the color stabillty compared toan untreated stock. It sulfur content is greater than [0%.

We have also discovered that the efficiency of sulfur removal for anygiven set of operating conditions can be markedly increased by blendinga relatively high sulfur content cracked gas oil with a relatively lowsulfur content cracked gas oil and processing as hereinabove described.

This additional embodiment of our invention is specifically illustratedin the following examples:

EXAMPLE 3 Two catalytically cracked gas oils, one from Middle East crudeand the other from West Texas crude were processed over cobalt molybdatecatalyst in the presence of hydrogen of 100% purity with the followingunexpected results:

llY DROREFINTNG CONDITIONS Temperature, F Charge 475 550 550 625Pressure, p.s.i.g Stock 350 350 650 500 LHSV, vjhrJv 0 6 6 6IIYDRODESULFURTZING STOCK A Wt. Percent bult'ur 1.06 1.02 1. 29 1.150.74 Percent S. Removal 2 22 31 65 HYDRODESULFIRIZING STOCK B Wt.Port-cut ult'ur 0. 0. 21 0.17 0.19 0. 12 Percent S. Removal 30 43 37 62CALCULATED RESULTS, FROM ABOVE DATA, OF A BLEND OF 1/3 A AND 2/3 B \\'t.Percent Hulfur 0. 75 0. 08 0. 54 O. 61 0. 33 Percent l e|noval ll 28 3256 ACTUAL RESULTS FROM TIYDRODESVLFURIZING A BLEND OF 1/3 A AND 2].; B

Wt. lorcvut Sulfur 0.75 0. 0S 0. 52 0. 0. 25 Percent S. Removal 11 31 4067 The above data show the remarkable benefit obtained by blending thetwo gas oils. For example, at 625 F., 500 p.s.i.g. and 6 LHSV, therelatively high sulfur content cracked gas oil was desulfurized and therelatively low sulfur content cracked gas oil was 62% desulfurized.Using these results, by calculation, a blend of 33% high sulfur stockwith 67% low sulfur stock should give 56% sulfur removal. However,actual desulfurization reached 67% which was 5% higher than the bestremoval obtained on an individual charge stock. It is noted that therelatively high sulfur content gas oil contained 1.36% more sulfur thanthe relatively low sulfur content gas oil. It should also be noted thatthis remarkable benefit was similarly achieved at other randomly pickedoperating conditions. However, it should be further noted that thebenefit of increased efficiency tends to disappear as the temperaturedrops below 500 F., e.g., at 475 F., there is no benefit from blendingthe feed stocks. On the other hand, as the temperature is increased, thedifference between the expected result and the actual result alsoincreases.

Thus. referring to FIGURE 1 and Example 3, it is seen again that thecritical temperatures of this invention lie between 500 F. and 675 F. Itis further noted in Example 3 that 33% by volume of relatively highsulfur content cracked gas oil can be blended with 67% relatively lowsulfur content cracked gas oil to achieve an unexpected benefit.

EXAMPLE 4 Several commercially available catalytically cracked gas oilswere treated over cobalt molybdate catalyst in the presence of hydrogenof 80% purity at a temperature 6 of 540 F., 750 p.s.i.g., and 5 LHSVwith the following results:

Percent Re- Percent Re- Percent Re- Chg. Wt. Percent moval PremovalPremoval Pre- Percent; Sulfur dleted from dicted from dicted from SulfurRemoval 0.6% dz 1.8% 0.6% & 1.4% 1.0% dz 1.8%

S Data S Date. S Data 49.5 A A A NOTE; A =difference between removalexperienced and removal calculated with a positive number indicatingthat the removal experienced. was greater than calculated.

The above results indicate, additionally, that the wider the differencein the sulfur contents of two charge stocks, the greater will be thesynergistic effect on desulfurization when desulfurizing a blend of thecharge stocks as opposed to desulfurizing the components individually.The amount of synergism which is obtained from any given blend isdependent upon the difference in sulfur contents of the two gas-oilswhich were blended. For example, it is seen from FIGURE 3, that thecalculated blends comprising a mixture of 0.6% sulfur and 1.8%

sulfur (diflerence=l.2%) are further from the actual results than eitherthe blend of 0.6% sulfur and 1.4% (dif ference=0.8%) or the blend of1.0% sulfur and 1.8% sulfur (difference:0.8% Therefore, the benefits ofthe present invention may be obtained if the relatively high sulfurcontent cracked gas oil contains from 0.5% to 5 0% more sulfur than therelatively low sulfur content cracked gas'oil.

The data from Examples 3 and 4 also indicate that the amount ofrelatively high sulfur content material which can be blended with therelatively low sulfur content material can vary from 25% to In Examples3 and 4, the minimum amount of high sulfur gas oil actually usedsuccessfully was 33% and in Example 4, the maximum amount used was 67%.

We claim:

1. Process for desulfurizing and increasing the color stability ofsulfur-containing cracked gas oil boiling mainly within the range of 425F. and 700 F. and containing at least 0.3% sulfur Which comprisescontacting in liquid phase said gas oil with a sulfur-resistanthydrogenation catalyst in an atmosphere of hydrogen in a contact zone,said contacting being eflected at a temperature from 500 F. to 675 F.,at a pressure from 300 p.s.i.g. to 1,000 p.s.i.g. and without any netflow of hydrogen vapor through said zone; and recovering a substantiallydesulfurized cracked gas oil of improved color and increased colorstability.

2. Process according to claim 1 wherein said temperature is from 550 F.to 650 F. and said pressure is from 500 p.s.i.g. to 800 p.s.i.g.

3. Process according to claim 2 wherein said catalyst is cobaltmolybdate supported on alumina.

4. Process according to claim 1 wherein said catalyst is cobaltmolybdate supported on alumina.

5. Process according to claim 1 wherein said cracked gas oil containsbetween about 1% and 3% sulfur.

6. Process for desnlfurizing and increasing the color stability ofsulfur-containing cracked gas oil boiling mainly within the range of 425F. and 700 F. and containing from about 1% to 1.75% sulfur whichcomprises passing said gas oil in trickle manner in a contact zone overa sulfur-resistant hydrogenation catalyst comprising cobalt molybdatesupported on alumina, in the presence of nonrecycle hydrogen added in anamount sufficient to make up for the hydrogen consumed, said contactingbeing effected at a temperature from 550 F. to 650 F., a pressure offrom 500 p.s.i.g. to 800 p.s.i.g, a liquid hourly space velocity of from0.5 to 10 and without any net flow of hydrogen vapor through said zone;and recovering a substantially desulfurized cracked gas oil of improvedcolor and increased color stability.

7. Process for desulfurizing and increasing the color stability ofsulfur-containing cracked gas oil boiling mainly within the range of 425F. and 700 P. which cornprises blending a relatively high sulfur contentcracked gas oil with a relatively low sulfur content cracked gas oil.the relatively high sulfur content gas oil containing from 0.5% to 5.0%more sulfur than the relatively low sulfur content gas oil; contactingthe blend with a sulfurresistant hydrogenation catalyst in an atmosphereof hydrogen in a contact zone, said contacting being effected at atemperature of from 500 F. to 675 F., a pressure from 300 p.s.i.g. to1,000 p.s .i.g., and without any net flow of hydrogen vapor through saidzone; and recovering a substantially desulfurizcd cracked gas oil ofimproved color and increased color stability.

8. Process according to claim 7 wherein said catalyst is cobaltmolybdate supported on alumina.

9. Process according to claim 7 wherein said relatively high sulfurcontent gas oil contains from 0.8% to 1.36% more sulfur than saidrelatively low sulfur content gas oil.

10. The process for desulfurizing and increasing the color stability ofsulfur-containing cracked gas oil boiling mainly within the range of 425F. and 700 F. which comprises blending from about 25% to 75% ofrelatively high sulfur content cracked gas oil with from about 75 7t:

to 25 relativelylow sulfur content cracked gas oil, the

relatively high sulfur content gas oil containing from 0.3% to 1.36%more sulfur than the relatively low sulfur content gas oil; passing theblend in trickle manner in a contact zone over .1; sulfur-resistanthydrogenation catalyst comprising cobalt molybdate supported on alumina,in the presence of non-recycle hydrogen added in an amount sufficient tomake up for the hydrogen consumed, said contacting being effected at atemperature from 550 F. to 650" F., a pressure of from 500 p.s.i.g. to800 p.s.i.g.. a liquid hourly space velocity of from 0.5 to 10 andwithout any net flow of hydrogen vapor through said zone and recoveringa substantially desulfurized cracked gas oil of improved color andincreased color stability.

References Cited by the Examiner UNITED STATES PATENTS 2,365,751 12/44Drennan 208143 2,608,521 8/52 Hoog 208254 2.697,683 12/54 Engel et al.208216 2.897.141 7/59 Honneycutt 20889 2.918.425 12/59 Berger et al zzzz 208108 2.022.759 1/60 Schlinger 208235 2.987,267 6/61 Keith et al.208211 ALPHONSO D. SULLIVAN, Primary Examiner.

MILTON STERMAN, Examiner.

1. PROCESS FOR DESULFURIZING AND INCREASING THE COLOR STABILTY OFSULFUR-CONTAINING CRACKED GAS OIL BOILING MAINLY WITHIN THE RANGE OF425*F. AND 700*F. AND CONTAINING AT LEAST 0.3% SULFUR WHICH COMPRISESCONTACTING IN LIQUID PHASE SAID GAS OIL WITH A SULFUR-RESISTANTHYDROGENATION CATALYST IN AN ATMOSPHERE OF HYDROGEN IN A CONTACT ZONESAID CONTACTING BEING EFFECTED AT A TEMPERATURE FROM 500*